With the digitization of electrical devices, various charging techniques and techniques for supplying power to these electrical devices have been proposed, and, in recent years, techniques have been attracting attention for non-contact charging using electromagnetic induction wherein when a current flows through a primary coil on one side, an electromotive force is generated in a secondary coil on the other side. In non-contact charging, the positional relationship between a shaft of the primary coil on the side of a charger and a shaft of the secondary coil on the side of a device to be charged affects electrical efficiency, and the electrical efficiency may be extremely low depending on the position or the orientation of the shafts of the coils.
For example, in the case of electric toothbrushes, non-contact charging is applied using electromagnetic induction. A non-contact charger for an electric toothbrush typically has a socket into which the electric toothbrush is to be placed such that the positions of (the shafts of) the coils are not significantly displaced from each other (i.e., such that electrical efficiency is improved), and partially holds the electric toothbrush while charging.
Furthermore, non-contact charging is also applied in the case of mobile phones, and a non-contact charger of a mobile phone also has a structure (a groove, etc.) that does not allow the mobile phone to move significantly. Here, a mobile phone has a vibration function, and, under particular settings such as silent mode (vibration mode), a user is notified of an incoming call by vibration instead of generation of a sound or light; thus, when there is an incoming call while charging, the mobile phone may move out of the charger due to the vibration. Thus, a technique is proposed whereby the vibration mode is forcibly cancelled during charging of a mobile phone, and the mode is returned to the vibration mode after charging of the mobile phone ends (Japanese Patent Laid-Open No. 2001-197674).
However, this conventional technology assumes only a situation in which one non-contact charger charges one device to be charged, and does not consider a situation wherein one charger simultaneously charges a plurality of devices to be charged. For example, in a case where a plurality of mobile phones are simultaneously charged, even when the vibration mode of one mobile phone is forcibly cancelled, if another mobile phone is in vibration mode, the entire charger may vibrate due to the vibration of given mobile phone. As a result, the positional relationship between the charger (primary coil) and each of the plurality of mobile phones (secondary coils) may be displaced, and, thus, efficient charging cannot be performed (i.e., the optimal positional relationship is lost, and charging efficiency is decreased).